Earth DNA deposited on Titan by Huygens?

Please excuse this naive query:

How is it possible to know that we have not just deposited some "earth
DNA" on Titan, via a single (or multiple) viral or bacterial
hitchhiker?

I realize that clean rooms are used for vehicle and instrument
fabrication, that heat of atmospheric entry, the 7 year transit time
and the radiological environment of interplanetary space all mitigate
against this possibility, but...

One compromised bacterium?
One (or a dozen, or a few hundred) virus/viruses?

And could someone point me to a discussion of this?
(Fresher than the period of manned lunar exploration.)

And is this now considered a trivial concern in the world of planetary
exploration?


Many thanks...

In article .com,
Smith wrote:
How is it possible to know that we have not just deposited some "earth
DNA" on Titan, via a single (or multiple) viral or bacterial
hitchhiker?

I would presume the opposite. Huygens was not sterilized.

From NASA Huygens Probe FAQ
http://saturn.jpl.nasa.gov/faq/huygens.cfm:

The Committee on Space Research (COSPAR), an interdisciplinary
committee of the International Council for Science, maintains a
consensus international planetary protection policy to be followed
by spacefaring nations. In 1988, the U.S. National Research
Council's Space Studies Board, working under COSPAR guidelines,
determined that the Cassini-Huygens mission fit into "Category II"
as follows:

"Category II missions comprise all types of missions to those target
bodies where there is significant interest relative to the process
of chemical evolution and the origin of life, but where there is
only a remote chance that contamination carried by a spacecraft
could jeopardize future exploration. The requirements are for simple
documentation only. Preparation of a short planetary protection plan
is required for these flight projects primarily to outline intended
or potential impact targets, brief pre? and post-launch analyses
detailing impact strategies, and a post-encounter and End-of-Mission
Report which will provide the location of impact if such an event
occurs. Solar system bodies considered to be classified as Category
II are listed in the Appendix to this document." For original
documents, see http://www.cosparhq.org/scistr/PPPPolicy.htm.

As a Category II mission, the Huygens Probe was not
sterilized. For more information on this, see this
European Space Agency web page on planetary protection:
http://www.esa.int/export/esaCP/ESAUB676K3D_Life_2.html

For information on NASA's planetary protection policies and
procedures, see http://planetaryprotection.nasa.gov/pp/index.htm.
--
Hud Nordin Silicon Valley

Smith wrote:
Please excuse this naive query:

How is it possible to know that we have not just deposited some "earth
DNA" on Titan, via a single (or multiple) viral or bacterial
hitchhiker?

How is it possible to care? I mean, nothing terrestrial is going to
*grow* there, so what the hell are you worrying about?

Paul

Smith wrote:
How is it possible to know that we have not
just deposited some "earth
DNA" on Titan, via a single (or multiple)
viral or bacterial hitchhiker?

I think it's a fairly good chance. AFAIK, Huygens
didn't get an extensive sterilization. But, I might
be wrong.

In any case, I say, "More power to any little bugger
that can survive on Titan."

If an Earth critter can prosper in cryogenic temperature,
a reducing atmosphere, and in a lack of sunlight, good
for it.

Mike Miller, Materials Engineer

In article .com,
Smith wrote:
How is it possible to know that we have not just deposited some "earth
DNA" on Titan, via a single (or multiple) viral or bacterial hitchhiker?

Well, it's not, because Huygens wasn't sterilized. There *have* been
sterilized spacecraft -- notably, the two Viking landers -- but it's a
difficult thing to do and it runs up the cost badly. Heat sterilization
is about the only fully effective method, and it's hard on electronics.

Modern practice is to sterilize only if (a) there are life-detection
experiments on board (which obviously might be confused by hitchhikers),
or (b) the destination environment is a place where Earth life might have
some chance of growing and spreading.

Almost certainly there *were* bacteria on Huygens at launch, and some of
them may even have still been technically viable on arrival.

Titan, interesting though it is, is *way way* too cold for Earth life.
(Temperatures not much colder than that are used for long-term pristine
*storage* of biological samples.) There is no realistic prospect of
hitchhiking organisms proliferating on Titan.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

Many thanks for your help (and patience) with my child-like query.

I proved my ignorance with the comments:

"One compromised bacterium?
One (or a dozen, or a few hundred) virus/viruses?"

It seems the standards (even for Mars) run into the 10s if not 100s of
thousands of micro-organisms as acceptable loads. But, to also answer
my own initial query, following the links provided I eventually found

http://www.astrobiology.com/protection.html

a site friendly (simple) enough to have probably precluded it in the
first place. Thanks.


I do find it curious though that the general response here seems that
as any earth organism would be unable to live/reproduce/thrive in such
an environment, consideration of their dispersal is rendered
uninteresting.


I suppose lurking in my uninformed thought was a notion of "earth
DNA" as potent information, even if not mechanically active. I
understand it is considered in the realm of possibility that bacterial
spores may possess integrity measured in "geologic" stretches...

"On the basis of such laboratory experiments, it has been proposed
that with proper shielding, bacterial spores might survive UV
irradiation for very long periods, perhaps millions of years."

from "Biological Contamination of Mars"
Space Studies Board / National Academy of Science
http://www7.nationalacademies.org/ssb/bcmarsch4.html



But I certainly don't mean to take up serious time here with what are
likely commonplace and perhaps adolescent wonderings. And I really
have no cranky axe to grind concerning this.

And if the last few decades might mark some potential exflorescence of
the terrestrial habit to the near and middle bodies of our solar
system, this hardly looms so very large in the wider view of things...
Thanks again.

Smith wrote:
Please excuse this naive query:

How is it possible to know that we have not just deposited some "earth
DNA" on Titan, via a single (or multiple) viral or bacterial
hitchhiker?
[...]

I realize that clean rooms are used for vehicle and instrument
fabrication, that heat of atmospheric entry, the 7 year transit time
and the radiological environment of interplanetary space all mitigate
against this possibility, but...

One compromised bacterium?
One (or a dozen, or a few hundred) virus/viruses?
How sure do you want to be before you think you "know"?

Lots of Greetings!
Volker

Smith wrote:

I do find it curious though that the general response here seems that
as any earth organism would be unable to live/reproduce/thrive in such
an environment, consideration of their dispersal is rendered
uninteresting.

I suppose lurking in my uninformed thought was a notion of "earth
DNA" as potent information, even if not mechanically active. I
understand it is considered in the realm of possibility that bacterial
spores may possess integrity measured in "geologic" stretches...

"On the basis of such laboratory experiments, it has been proposed
that with proper shielding, bacterial spores might survive UV
irradiation for very long periods, perhaps millions of years."

I've always felt that the two possible answers to the question of is
there life in the rest of the universe is either "yes" or "not yet". If
we can't find it, then at some point we should start spreading it. Take
a big blob of primordial hydrocarbon feasting ooze and put it into an
armored bunker-buster casing and drop it on Titan in a probe that would
survive an impact and burrow into the surface. And just let it do it's
thing.

[[ This message was both posted and mailed: see
the "To," "Cc," and "Newsgroups" headers for details. ]]

Henry,

My concern here is what happens when you dump RNA and DNA into a
reducing soup containing amino acids at whatever temperature.
Sometimes, or so I understand, the RNA and DNA replicate even without
an enclosing cell. This could actually make a global change to the
chemistry of Titan, if it could occur under those conditions. Proteins
can sometimes self-replicate, too. This could cause a sort of
molecular evolution to begin there. Not life-as-we-know-it, certainly,
but it would be very interesting should it happen...

-Ben Burch

In article , Henry Spencer
wrote:

Titan, interesting though it is, is *way way* too cold for Earth life.
(Temperatures not much colder than that are used for long-term pristine
*storage* of biological samples.) There is no realistic prospect of
hitchhiking organisms proliferating on Titan.

In article ,
Ben Burch wrote:
My concern here is what happens when you dump RNA and DNA into a
reducing soup containing amino acids at whatever temperature.
Sometimes, or so I understand, the RNA and DNA replicate even without
an enclosing cell...

DNA needs a complex set of supporting machinery to replicate. RNA can
replicate by itself, although somewhat imperfectly, given a supply of
bases. (Those are not amino acids; amino acids are what make up
*proteins*, not nucleic acids like RNA.)

However, RNA can and does appear spontaneously given a supply of bases.
If there are substantial supplies of suitable raw materials sloshing
around on Titan, then there will already be RNA present... and it will be
evolved to suit conditions (yes, RNA can evolve, in simple ways) much
better than any random Earth RNA would be.

This could actually make a global change to the
chemistry of Titan, if it could occur under those conditions. Proteins
can sometimes self-replicate, too. This could cause a sort of
molecular evolution to begin there...

Again, if suitable conditions exist, then almost certainly they have
existed for long enough for such a development to start spontaneously.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |